The International Space Station is as gross as your own home

When you think of the International Space Station — that huge floating laboratory cruising through Earth’s atmosphere that has housed dozens of different astronauts and cosmonauts over the years — what image does your mind paint? If it’s a picture of pristine, almost clinical cleanliness, far away from the grime that you already know covers your kitchen counters and couch cushions, you should think again.

A new study published in the journal PeerJ reveals that the inside of the International Space Station is actually teeming with microbial life and now after 17 years in use and without a single housekeeping visit, as many as 4,000 or more species of microbes can now be found inside. It might sound mighty nasty, but believe it or not, it’s actually good news.

The samples used in the project were taken a few years back as part of an experiment which sent microbe swabs from various sports stadiums to the space station. Researchers wanted to see if the microbes would grow in the zero gravity environment of the ISS and in return, the ISS crew swabbed their own living quarters and sent those swabs back to Earth for testing.

Taken from 15 different spots around the space station, the swabs contained between 1,036 and 4,294 different microbe species. That wide range is due to the inexact nature of classifying microbes, which sometimes results in similar organisms being classified as different when they’re actually the same.

Regardless of that very rough estimation, it’s clear that there’s plenty of microscopic organisms that call the International Space Station home and scientists are more or less okay with that fact. “Diversity is generally associated with a healthy ecosystem,” lead author and UC-Davis microbiologist David Coil explains, adding that the discovery was “reassuring.”

With that number of microbes hanging out on various surfaces within the space station, the orbiting laboratory actually compares quite nicely with the average human home. The microbes present in the station all likely came from human hosts, which is why the species identified are the same you’d be likely to find on a typical human. So, if you’re ever feeling like your living room is just gross, at least you can say that it’s as clean as the ISS, or close to it.